Presently, the broadband access techniques mainly include copper cable access techniques (e.g., various DSL techniques) and optical access techniques. Access networks implemented with optical access techniques are referred to as Optical Access Networks (OANs).
PON technique is a point-to-multi-point optical access technique. FIG. 1 is a schematic diagram of the PON system. The PON system includes Optical Line Terminals (OLT), Optical Distribute Network (ODN), and Optical Network Units (ONUs); wherein, OLT provides a Service Node Interface (SNI) for OAN to connect one or more ODNs; ODN transmits downlink data from OLT to each ONU through optical paths; similarly, ODN transmits the uplink data from ONUs to OLT by convergence; ONU provides an User Network Interface (UNI) for OAN and is connected to ODN; if ONU also provides user port function (e.g., Ethernet user port or Plain Old Telephone Service (POTS) user port), it is referred to as an Optical Network Termination (ONT). Unless otherwise specified, hereunder ONU and ONT are referred to as ONT collectively.
In relevant BPON and GPON standards, the model of ONT configuration and management by OLT is defined. OLT manages ONTs via the ONU Management and Control Interface (OMCI) channel. OMCI is the master/slave management protocol, in which the OLT is the master device and ONT is the slave device; OLT controls multiple ONT connected thereunder through the OMCI channel. In a local area network (LAN), sometimes it is necessary to isolate the traffic between users, and to restrict the size of broadcast domain; these functions can be implemented through a Virtual Local Area Network (VLAN). Specifically, a VLAN Tag layer can be added to the users' Ethernet messages; Ethernet frames added with VLAN Tag can only be forwarded within the VLAN. The structure of Ethernet frame added with VLAN Tag is shown in FIG. 2.
The value of a Tag Protocol Identifier (TPID) is fixed to 0x8100; the value of Tag Control Information (TCI) is determined in accordance with the strategy for adding VLAN ID to a specified Ethernet port; TCI includes Priority Code Point (CPC, which is VLAN Priority), Canonical Format Indicator (CFI), and VLAN Identifier (VID).
With the PON technique for user access, in order to isolate the traffic between users or between different services of the same user, different VLANs have to be segmented for each user or for different services of the same user. Hereunder we describe how ONT adds the Ethernet message with a VLAN Tag and then transmits the Ethernet message received via the User Network Interface (UNI) to OLT. As shown in FIG. 3., first, the ONT receives an Ethernet message without a VLAN Tag via the UNI; next, the Medium Access Control (MAC) bridge module in the ONT adds a VLAN Tag to the Ethernet message, and then transmits the Ethernet message to the GPON protocol processing module via the internal Ethernet port; finally, the GPON protocol processing module adds necessary GPON protocol header information to the received Ethernet message to create a GPON frame, and then sends the GPON frame to OLT.
Still in the example of GPON, OMCI is a configuration transmission channel defined in GPON protocol. In the GPON protocol, the data of the ONTs managed by OLT are abstracted into a protocol-independent Management Information Base (MIB), the basic information unit of which is Managed Entity (ME). In the BPON/GPON standard, the ME that manages the VLAN Tagging operations at the ONT Ethernet port is defined as follows:
ME: VLAN Tagging Operation Configuration Data.
Data relationship: each instance of ME for the VLAN Tagging operation configuration data corresponds to a physical Ethernet port of ONT, the physical Ethernet port managed by a Physical Path Termination Point Ethernet UNI ME. The attributes of the ME is shown in the following table:
ME IDThis attribute provides a unique numbered ID for each instance of theME; the numbered ID is identical with the numbered ID of Physical PathTermination Point Ethernet UNI ME. (Read only, set during creation)(required) (2 bytes)Uplink VLANThis attribute indicates whether the uplink Ethernet frame has a VLANTaggingTag.operation mode0x00: No VLAN Tagging operation for the uplink Ethernet frame, nomatter whether the Ethernet frame carries a VLAN Tag or not;0x01: Add a VLAN Tag to the uplink Ethernet frame; if the Ethernetframe doesn't carry a Tag, add a VLAN Tag in accordance with the“uplink VLAN Tag TCI value”; if the Ethernet frame carries a Tag,modify the data in TCI field carried in the Ethernet frame in accordancewith the “uplink VLAN Tag TCI value”;0x02: Add a VLAN Tag to the uplink Ethernet frame; if the Ethernetframe carries a Tag, add a second layer of VLAN Tag in accordance withthe “uplink VLAN Tag TCI value”; if the Ethernet frame doesn't carry aTag, add a VLAN Tag layer in accordance with the “uplink VLAN TagTCI value”;(Readable, writeable, set during creation) (required) (1 byte)Uplink VLANThe value of uplink VLAN Tag TCI; apply the field if the operation modeTag TCI valueof uplink VLAN Tag is 0x01 or 0x02.(Readable, writeable, set during creation) (required) (2 bytes)Downlink VLANThe downlink VLAN Tagging operation mode,Tagging0x00 indicates no operation.operation mode0x01 indicates removing the Tag from the downlink Ethernet frame.(Readable, writeable, set during creation) (mandatory) (1 byte)
For example, in the GPON standard, if the uplink VLAN Tagging Operation Mode attribute is set to 0x01, ONT will process the received Ethernet message via the Ethernet port at user side in a way shown in FIG. 4. In that mode, ONT will add a preset VLAN Tag layer to the message without a VLAN Tag received via the Ethernet port at user side; the ONT will replace the existing VLAN Tag with a preset VLAN Tag for the message added with a VLAN Tag, so that the Ethernet messages forwarded by the MAC bridge module in uplink direction have a uniform outermost VLAN Tag layer; in other words, all VLAN Tags contained in all uplink Ethernet messages are the same after they are processed by ONT through the VLAN Tagging operation, similar to the “V0” shown in the Figure.
In the GPON standard, if the uplink VLAN Tagging Operation Mode attribute is set to 0x02, ONT will process the received Ethernet message via the Ethernet port at user side in a way shown in FIG. 5. The ONT will add a preset VLAN Tag layer to the message without VLAN Tag received via the Ethernet port at user side; it will add a second VLAN Tag layer to the message added with a VLAN Tag in accordance with the “uplink VLAN Tag TCI value”, all Ethernet messages forwarded by the MAC bridge module in the uplink direction have a uniform outermost VLAN Tag layer, i.e., VLAN Tags contained in all uplink Ethernet message are the same after they are processed by the ONT through the VLAN Tagging operation, similar to the “V0” shown in the Figure.
During the process that the present invention is implemented, the inventor has found, existing ONTs can only add a same VLAN Tag to the messages received via the same Ethernet port at user side. Usually, in an optical network, other network devices that are interconnected with the ONT and designed to perform subsequent processing for messages from the ONT will perform subsequent processing in accordance with the VLAN Tag added by the ONT to the messages. Therefore, if the ONT adds the same VLAN Tag to all received messages, the subsequent network devices can only perform the same processing for the messages when the messages from the ONT enter into the subsequent network devices; however, such a simple processing method can't meet diversified demands for processing any more.